Further studies of the thalamic afferents fiber from the posterior column and superior cerebellar peduncle show in chimpanzee that they initially enter the posterior and anterior portions of the n. ventralis posterior (VP) respectively rather than the VP and n. ventralis lateralis. In a human case, a discrete thalamotomy on one side entered the posterior part of VP (n. ventrocaudalis) producing contralateral paresthesias. A lesion in the anterior part of VP (n. ventrointermedius) resulted in no subjective sensory change supporting the non-sensory nature of this portion of VP in man. Stimulation of the supplementary motor area in man produced the expected contraversive gross muscular synergies, but paramedian stimulation failed to elicit the classical contraversive movements of the head. Frequent sensory responses were found most frequently involving large areas or ipisilateral regions of the body. These new findings may assist the interpretation of clinical seizure phenomena.